Zone refining apparatus



2,937316- ZONEIIREFINING APPARATUS Robert 'W'. Fritts, Elm Grove, Wis., and Sebastian Karrer,

Port Republic, Md., assiguors', by meme-assignments, to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Application December 30, 1957, Serial No. 706,173 r '11 Claims. curs -1 Zone refining-or zone purification as itis'sometimes called; is a process commonly associated with therpuri fication of metals of alloys. -This process exploits the. phenomenon occurring upon freezing of a liquid containing impurities, whereby the differences in solubilitiesof the impurity and in the diffusion rates in the liquid phase:

versus the solid phase cause the impurities to tend to concentrate in the liquid phase as solidification proceeds.- :As; a result, the solidified phase has a reduced impurity.

content. a

The process of zone refining is not limited to use in the purification of metals or alloys, but is equally useful for the purification of substances that are in a liquid state at'ordinary temperatures. With this in mind 'it is a general object of the present invention to provide improved apparatus for zone refining which operates in a manner U tc S a Paten .0."

to take advantage of the particular adaptability of thermo- I V lectric,"i.e.,; Peltier, heat pumps in carrying out the zone refining operation.

Another object of the invention is to provide an improved zone refiningapparatusof the class described which is highly efficient in operation by virtue of the fact that in said apparatus there is no' 'substantial loss of the heat of fusion of the material refined.

- A more specific object of the invention is to provide an improved zone refining apparatus of the aforemen tioned character having embodied therein thermoelectric heat pump means having heat emitting and heat absorbing thermojunction means in good heat transfer relation with the material to be-refined, the heat emitted at f the' heat emitting .thermojunction means being operableito e'liect liquefication of a zone of the material tobe refined,

' and theheat absorbed at the heatabsorbing thermojunction means being operable to cool the material adjacent thereto for solidification thereof, such'thatboth the heat- 1 ing and the cooling effect of the thermoelectric heat pump means is utilized to' advantage for maximum efliciency. Q

Another object ofthe invention is'to provide an improved zone refining apparatus which is, adaptable for'the zone refining of'materials the liquid phase of which has relatively high electrical conductivity as well as for materials the liquid phaseof which has relatively low electrical conductivity. f I

A further object of the invention is to providelan improved zone refining apparatus wherein the rate of progression of the thermoelectric heat pump means thereofalong the body'of material to'be refined is automatically controlled by the 'rate at which the heat emitted at the heat emitting. 'thermojunction means'thereof effectsv lique'fication of'said material. v t

7 Other and further objects and advantages of the inven tion will'become apparent as the description proceeds,

f Figure l is a fragmentary perspective view of one form of improved zone'refining apparatus, parts being broken away;

reference being had to the drawing accompanying and v forming a part of this specification wherein:

; -Figure 2. is a fragmentary perspectiveview of another form of improved zone refining apparatus parts'be ng:

broken away; and 1 A Figure 3 is a wiring diagram of the electrical circuit of the apparatus shown in Figure 2.

Referring more particularly to Figure l'of the drawing,

the numeral 5 indicates an elongated open-topped receptacle of rectangular configuration made of plastic or some other poor thermal conductor adapted to contain afma-J' terial to be refined by the improved apparatus Disposed"- 1 within the receptacle 5 and spaced out of contact with H Y the side and bottom walls thereof by supporting means to be described hereinafter, is thermoelectric heat pump means 6 comprising a thermoelement 7 which may takethe form of a rectangular block of semi-metallic material junction members or plates 8 and 9 are angled inwardly and thence upwardly to provide flangesltl andl 11 by I means of which the plates 8 and 9 are respectively aflixed to a supporting member 12*of low thermal' and electrical conductivity. Means, for example; the conductors 13 and 14 shown schematically, is provided for connectingthe thermojunction members 8 and 9 in circuit with the terminals of a source 15 of direct current.

Means is provided for effecting endwise' movement of the thermoelectric heat pump 6 longitudinally :of the.

receptacle 5, as well as for supporting saidheat pump means within the receptacle. The illustrated form of said means comprises an elongated screw '16 spacediaboveg' the receptacle 5, in longitudinal alignment therewith, and

parallel with the bottom wall thereof. The screw 16 is journaled in suitable bearings 17v and 18 permittingrota tion of said shaft and lifting thereof from said bearings while preventing substantial axial movement of said shaft; A block 19 is' formed with an internally-threadedbore 20 and is threaded on the screw 16.;Theblock '19 and the supporting member 12 are formed'with cooperating meansrfor removably connecting the member 12 to said block for dependencetherefrom. Inthe illustrated fem-i bodiment, the. connecting means takes the form-of an upper end portion of T-shaped cross-section formed on the member 12, said portion being removably disposed within a complemental T-shaped groovell formedlon" the underside of the block 19 as shown. v

The screw 16 is provided with suitable means tending to cause rotation thereof, and thereby longitudinal move ment of the block 19 and heat pump means 6, along the screw 16 and receptacle 5. In the embodimentillus trated in Figure 1 the aforementioned. means comprises a drum 22 fixed on the screw 16 and adapted to' have a suitable flexible cord 23 or rope wound thereon'iandj v anchored-thereto at one end.. The other end of thelcord g 23 has a weight 24 suspended therefrom and tending to cause rotation .of the drum 22'and screw 16in'a clock wise-direction as viewed from' the left-hand end ofsthe screw.

of a material which exhibits a high Pel'tierf'coefiicient,

low' thermal: conductivity and low electrical resistivity. V

More specifically, the thermoelement 7, may be'made of one of the materials described in our copending-application, Serial Number 512,43 6', filed Ju'ne'l; l9i55, and assigned to the assignee of'the present application. 1 Such materials are alloys comprising lead and at least one member of the group tellurium, selenium and sulphurand 2,937,216 7 a. m d- 17? 1 It is desirable that the heat pump thermoelement-7' be include semi-metallic alloys or compositions which may be characterized as binary metallic compounds of slightly imperfect composition, i.e., containing beneficial impurities constituting departures from perfect stoichi-- ometry by reason of an excess of one of the metals over the other and/or containing added beneficial impurity substances. The thermoelement 7 may also be made of an alloy or composition comprising a mixture of the aforementioned binary metallic compounds which may be termed a ternary metallic alloy or composition. Certain of these alloys or compositions exhibit negative and certain exhibit positive electrical characteristics, and for the thermoelement 7, it is immaterial whether the specific material selected is P type or N type, as long as the current flow therethrough is in the proper direction to accomplish the desired function.

The current flow through a thermoelement which exhibits positive electrical characteristics causes heat to be pumped in the direction of current flow therethrough, whereas current flow through a thermoelement which exhibits negative electrical characteristics causes heat to be pumped in the direction opposite to the direction of current flow therethrough. Thus, in the embodiment illustrated in Figure 1, if the thermoelement 7 is of the P type, it is necessary for proper operation of the apparatus, that the current flow from the thermojunction member 9 through the thermoelement 7 toward the thermojunction member 8, so that heat will be pumped from the thermojunction member 9 to the thermojunction member 8. On the other hand, when the thermoelement 7 is of the N type, it is necessary for proper operation of the apparatus that the current flow through the thermoelement from the thermojunction member 8 toward the thermojunction member 9, so that heat is pumped through the thermoelement 7 from the thermojunction member 9 to the thermojunction member 8.

The operation of the form of the invention illustrated in Figure 1 will now be described. The screw 16 and drum 22 are rotated by any suitable means in a counterclockwise direction as viewed from the left-hand end of the screw to thereby move the block 19 and the heat pump means 6 to the right-hand end of the receptacle 5, as viewed in Figure l, and also to wind the cord 23 on the drum 22. The material to be purified is prepared in solid. form, i.e., liquids must be frozen, and the frozen block or ingot of material is placed in the receptacle 5 to the left of the heat pump means 6. The apparatus is operated in an ambient temperature which is preferably substantially below the freezing point of the materials to be refined, any suitable equipment, not shown, being used to provide the desired ambient temperature.

Direct current from the source 15 is caused to flow through the heat pump 6 in the direction to cause heat to be absorbed at the thermojunction between the member 9 and the thermoelement 7 and to be pumped to the thermojunction between the member 8 and said thermoelement for liberation at the member 8. In addition to the heat thus pumped, heat produced by dissipation of electrical energy within the heat pump means 6 is also liberated at the member 8. This, of course, provides heating at the member 8, causing a zone of thesolid material adjacent the member 8 to be liquefied.

The weight 24 provides a continual bias which, acting through the drum 22, screw 16 and block 19, continually biases heat pump means 6 toward the left, as viewed in Figure 1, so that as the solid material adjacent the thermojunction member 8 liquefies, the heat pump 6 is advanced toward the left, and the liquefied portion of the material is displaced around the sides and bottom of said heat pump, into engagement with the heat absorbing thermojunction member 9. The absorption of heat at the thermojunction member 9, together with the cooling effect of the reduced ambient temperature, provides for progressive solidification of the displaced liquid phase as the heat pump moves along the length of the receptacle 5. Because of the difference in solubilities of the impurity and in diffusion rates in the liquid versus the solid phase, the molten zone tends to concentrate the impurities of the material, leaving the refrozen material behind the heat pump 6 with a'reduced impurity content.

Since there is normally a continuously molten zone surrounding the heat pump 6 throughout its course of travel from the right-hand end to the left-hand end of the receptacle 5, said molten zone has a high concentration of impurity therein by the time the heat pump means 6 reaches the left-hand end of the receptacle. At this point, the heat pump 6 can be removed from the receptacle 5 by lifting the screw 16 from the bearings 17 and 18, or by lowering the receptacle, the impurity laden liquid phase remaining at the left-hand end of the receptacle '5,'from which it can be removed inany desired and suitable manner. The solid phase of the material remaining in the receptacle 5 has a substantially reduced impurity content.

The heat pump 6 preferably operates with an absorption junction temperature substantially equal to the melting temperature of the solid phase containing the impurity. This temperature may be higher than the freezing point of the liquid phase, due to the usual point suppression observed with many solvent-solute systems, e.g. salt in water.

Due to the fact that the major portion of the heat emitted at thermojunction member 8 is heat which is absorbed at the thermojunction member 9, there is no substantial loss of the heat of transformation of the material refined, and highly efiicient operation is provided, in contradistinction to the relatively low efficiency of an apparatus which employs conventional electrical resistance or induction type heating means for etfecting liquefication and zone refining.

The improved apparatus can be used to refine any material having a melting point within the operating range of the thermoelectric heat pump means 6. The upper limit on the temperature at which the improved apparatus can operate is that which would tend to cause melting of the thermoelement 7 or disintegration of the bond between said thermoelement and thermojunction members '8 and 9.

Figure 2 illustrates a form of the invention which is particularly Well adapted for the zone refining of material which in its liquid phase has relatively high electrical conductivity. The apparatus shown in Figure 2 utilizes two receptacles 5a and 5b which may be similar to the receptacle Swot Figure 1 and which are preferably made of material having low electrical conductivity and high thermal conductivity, for example, glass or certain plastics. The receptacles 5a and 5b are preferably disposed in longitudinally offset spaced parallel relationship, and have parallel planar oppositely disposed external side wall surfaces 25a and 25b respectively. Interposed between the receptacles 5a and 5b, with opposite end surfaces in sliding and good thermal contact with the surfaces 25a and 25b of said receptacles is heat pump means in the form of a plurality of thermoelectric pumps, four of which, numbered 26, 27, 28 and 29, are illustrated. Referring to Figure 3, the heat pumps 26, 27, 28 and 29 each comprise a P type thermoelement 30 and an N type thermoelement 31, each of which may be made of a semi-metallic material of the character referred to hereinbefore in describing the thermoelement 7 of Figure 1. The thermoelements of the heat pumps 26 and 28 are bonded, as by soldering, to and electrically joined by thermojunction members 32 and the thermoelements of the heat pumps 27 and 29 are similarly bonded to and electrically joined by thermojunction members 33. Bond- .ed to the opposite ends of the thermoelernents 30 and 31 of the heat pumps 26 and 28 are thermojunction members 35 .and 36.. Bonded to. the opposite ends of the by screws.

. thermoelements 30 and 31- of heat'pumps 2 7 and 29 are thermojunction members 37 and 38.! j

Means is provided, for supporting and actuating the heat pumps 26 to 29, said means; in the embodiment il- 'lustrated in Figure 2 taking the form of a rack member Each of the heat pumps is supported on the rack mem:

ber 41 in a similar manner, the mounting of heat pump 27 being the only one shown and described in detail. As shown in Figure 2, a supporting member 43 of material having low electrical and, thermal conductivity may be generally I-shaped in cross-section and has its lower end suitably fixed to the rack member'41, for example, The thermojunction member joining the thermoelements of the heat pump, i.e., the member, 32 ofthe heat pump 26, takes the form of a plate the lower edgeof which is inturned and overlaps one side of the upper end of thesupporting member 43 in. fixed rela- :tion thereto. The thermojunction members at the opporsite ends of the thermoelements fromthe joining thermoe junction member, i.e., the members 35 and,36' of the heat pump 26, take the form of a Z-bar in end view,

I.-;so,that the lower end thereofis inturned'and overlaps Ithe other side of the upper end of the member 43, said members 35 and 36 each terminating in a lower end,

hers 33, 35 and 36 slidingly engage the receptacle surface 25b in good thermal contact. Conductors 44 and L45, connect the thermojunction member 35 of heat pump 26 and 38 of heat pump 29 respectively with a source 46 of direct current. The heat pumps 26 to 2 9.are connected in seriescircuit by conductors 46, 47 and 34, which respectively connect thermojunction member, 36 of heat pump 26 to thermojunction member 37 of heat pump 27; thermojunction member 38 of heat pump 27 to thermojunction member 35 of heat pump 28; and thermojunci tion member 36 of heat pump 28 to thermojunction member, 37, of heat pump 29. A manually operated switch .48, may be interposed in conductor 45 for control of the 'energization of the heat pumps 26 to 29. .jMeans is provided for. effecting actuation of the rack 41, and of the heat pumps 26 to 29 supported thereon. The actuating means illustrated in Figure 2 takes the form of a motor 49 having a speed-reducing unit embodied V .thereinand having a power take-off shaft 50 which rotates very slowly. The drive shaft 50 is connected byway I of a one-way clutch 51 to a shaft 52 on which a pinion 53 is keyed, said pinion meshing with the teeth of the rack 41 as shown. The motor 49 may be connected with a suitable source of electrical energy, for example the alv' -ternating current source 54, by means of conductors 55 audl'56. As shown, a switch 59 may beinterposed in the ,conductor 55 for control of'the energization of the motori49.

I 2 The operation of the apparatus shown in Figure 2'will 'now be described. The material to be purified is prepared in solid form and placed within the receptacles j :aand5b preferablya's solid bodies'or ingots 57 and 58.

If desired, the material may be placed within the recep- -tacles 5a and 5b in liquid form and frozen; therein. 'As with the form of theinvention shown'in Figure '1,

' :the operation of theapparatus shown in Figure 245 car- 3 fied out in an ambienttemperaturebelow the freezing point of the material to be purified, andfany suitable equipment (not shown) may be utilized forproviding;

thenecessary ambient temperature. To place the iimproved apparatusinto operation, the rack 41 and heat pumps 26 to 29 are moved toward the right," for example manually, to extremity of their travel in that direc tion, to thereby bring the heat pump 29 adjacent the right-hand end of the receptacle 5a, and the heat pump' 28 adjacent the right-hand end of the receptacle 5b; This movement of the rack 41 and the heat pumps can be accomplished rapidly, since the one-way clutch 51 permits i free rotation of the pinion 53 in the direction opposite the driving direction of the motor 49. The switch 48 is then closed to cause direct current from the. source-46 to flow serially through theheat pumps 29, 28, 27 and] 26 in the direction indicated by the solid arrows' in Fig; ure 3. More specifically, the currentflows through the heat pump 29 from thermojunction member 38 to thermojunction member 37, throughheat pump 28 from f thermojunction member 36 to thermojunction member 35, through heat pump 27;from thermojunctionmember 38 to thermojunction member, 37, and through heat pump. 1 26 from thermojunction member 36 to thermojunction terial 57 in the receptacle 5a at ,the thermojunctiongmembers 32 by means of thermaloconduction;through the y receptacle wall having surface 25a in contact "with said I thermojunction members. This heat, plus heat resulting from the dissipation of electrical energy within the heat pump 27 is emitted from ,the heat pumps 26' and 28 at the thermojunction members 35 and 36 and is' conducted through the receptacle Wall havingsurface 25b in con tact with said thermojunction members to the material 58. The heat pumps 27 and 29 operate to absorb heat from the material 58 at thermojunction members 33 and31 by conduction through the contactingwall portions of V the receptacle 5b and emits said heat, plus heat resulting I from the dissipation of electrical energy within said heat 7 pumps, at thermojunction members 37 and 38 for con- .du'ction through the contacting wall portions ofthe re ceptacle 5a to the material 57. v

The pumping of heat by the energizedheat pumps 26 to 29 in-the directions indicated causes liquefactionof a zone of the material 58 adjacent thermojunctionmem bers 35 and 36 of each of the heat'pumps 26 and 28, and also causes liquefaction of a zone of the mate rial 57 adjacent thermojunction members-37 and 38 of each ot the heat pumps 27 and 29. Once the liquefied zones. have grown to "extend transversely across the re spect-ivebodies of material 57 and 58 the-motor switch 59. is closed to cause the rotation of the shaft 50, clutch 51, shaft 52 and, pinion 53 at a very slow rate in the 'direction indicated by the arrow. This causesthe rack 41 and the heat pumps 26 to 29 mounted" thereon to .move slowly toward the left, as viewed in Figure 2, and as the heat pumps so move, the boundaries of the liquefied zones migrate correspondingly withithe -heat I emitting thermojunction members 35, 36, 37* and 38 thereadjacent. As the heat pumps so move, .hgwever, it Will be noted that the heat absorbing thermojunction members 32 and 33 of the heat pumps cool, and with. the cooling effect of the reduced ambient temperature.

Operation of the motor 49 is continued until the heat' pumps 26 and 27 respectively arrive at the left-hand ends of the receptacles b and 5a, respectively, in the positions shown in Figure 2. It will be noted that when the heat pumps 26 to 29 are in the positions shown in Figure 2, there is a liquid zone in the material 57 adjacent the heat pump 27, as well as adjacent the heat pump 29. It will also be noted that there is a liquid zone in the material 58 adjacent the heat pump 26, as well as adjacent the heat pump 28. Alternated with the liquefied zones aforementioned, are zones of solidified material. More specifically, as in Figure 2, the solidified zones in the material 57 are adjacent the heat pump 28 and adjacent the right-hand end of receptacle 50, whereas in the material 58 the solidified zones are adjacent the heat pumps 27 and 29. As aforementioned, solidification of the materials 57 and 58 is efiected by absorption of heat at the heat absorbing thermojunction members 32 and 33, as well as by the cooling effect of the reduced ambient temperature.

Upon arrival of the heat pumps 26 to 29 at their positions shown in Figure 2, the switches 5? and 48 are opened, and the rack 41 and said heat pumps are reset to their right-hand limit position aforementioned in preparation for a new cycle. On resetting, the heat pumps 26 and 27 may assume the positions occupied by the heat pumps 28 and 29 respectively shown in Figure 2, so that the heat emitting thermojunction members of the heat pumps 26 and 27, upon being reset, are each disposed adjacent a liquefied zone within the receptacles 5a and 5b.

Upon closure of the switch 4-8, and subsequent closure of the motor switch 59, the cycle may be repeated to cause progressive migration of liquefied zones of the materials 57 and 58 toward the left-hand end of the receptacles 5a and 5b. Any desired number of cycles may be carried out, and at the end of the final cycle, the liquefied zones at the left-hand ends of the receptacles 5a and 5b, which now have a high concentration of impurity therein, may be removed from the receptacles 5a and 5b in any desired manner, leaving the remainder of the material 57 and 58 with reduced impurity content.

Having thus described two specific embodiments of the improved zone refining apparatus, it is to be understood that the illustrated forms were selected to facilitate the disclosure of the invention, rather than to limit the number of forms which it may assume. Various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention, and all of such modifications, adaptations and alterations are contemplated as may come within the scope of the appended claims.

What is claimed as the invention is:

1. Apparatus for zone refining of a body of solid material comprising, thermoelectric heat pump means having heat emitting thermojunction means in good heat transfer relation with said body to afford liquefication of a Zone of said material adjacent said thermojunction means, and means for causing gradual relative movement of said thermojunction means and said body in a direction to effect gradual progression of said liquefied zone through said body.

2. Apparatus for zone refining of a body of solid mamojunction means to efiect liquefication of a zone of said material adjacent said first thermojunction means.

3. Apparatus for zone refining of a body of solid material comprising,thermoelectric heat pump means having heat emitting thermojunction means in good heat transfer relation with said body and having heat absorbing thermojunction means in good heat transfer relation with said body at 'a point spaced from said heat emitting thermojunction means, and means for causing gradual relative movement of said heat pump means and said body along a line substantially parallel with the spacing between said thermojunction means and in a direction to effect gradual progression of said heat emitting thermojunction means along said body ahead of said heat absorbing thermojunction means.

4. In apparatus for zone refining of a body of solid material without substantial loss of the latent heat of fusion of said material, a thermoelectric heat pump having a heat emitting first thermojunction in good heat trans fer relation with said body and having a heat absorbing second thermojunction in good heat transfer relation with said body at a point spaced from said first thermojunction, and means mounting said body and heat pump means for relative movement in the direction of the spacing between said first and second thermojunction, said heat pump being operable when energized to absorb heat from said body at said second thermojunction and to pump said heat to said first thermojunction for emission thereat to effect liquefication of a zone of said material adjacent said first thermojunction.

5. Apparatus for zone refining of a body of solid material without substantial loss of the latent heat of fusion of said material comprising, a thermoelectric heat pump having a heat emitting first thermojunction in good heat transfer relation with said body and having a heat absorbing second thermojunction in good heat transfer re lation with said body at a point spaced from said first thermojunction, said heat pump being operable when energized to absorb heat from said body at said second thermojunction and to pump said heat to said first thermojunction for emission thereat to effect liquefication of a zone of said material adjacent said first thermojunction, and means for causing gradual relative movement of said heat pump and said body in the direction of the spacing between said first and second thermojunction to effect gradual progression of said heat emitting thermojunction along said body ahead of said heat absorbing thermounction.

6. In apparatus for zone refining of a body of solid material without substantial loss of the latent heat of fusion of said material, a receptacle for said material, a thermoelectric heat pump mounted for endwise movement within said receptacle comprising a thermoelement having means at one end forming a heat emitting first thermojun'ctionin good thermal contact with said material and having means at the opposite end forming a heat absorbing second thermojunction in good thermal contact with said material, said heat pump being operable when energized to absorb heat from said body at said second thermojunction and to pump said heat to said first thermojunction =for emission thereat to effect liquefication of a zone of said material at said first thermojunction.

7. Appartus for zone refining'of a body of solid material comprising, a receptacle for said material, a thermoelectric heat pump within'said receptacle comprising a thermoelementhaving means at one end forming a heat emitting first thermojunction in good thermal contact with said material and having means at the opposite end forming a heat absorbing second thermojunction in good thermal contact with said material, said heat pump being operable when energized to absorb heat from said body at said second thermojunction and to pump said heat to said first thermojunction for emission thereat to effect .liquefication of a zone of said material at said first thermojunction, and means for effecting gradual movement of said heat pump within said receptacle endwise of, said thermoelement and in the'direction of said one end of the latter.

heat pump means mounted for relative movement longitudinally of said bodies and having heat emitting thermo- "junc tion means in good heat transfer relation with one 1 of; said bodies and having heat absorbing thermojunction means in good heat transfer relation with the other a of said bodies, said first heat pump means being operable when energized to absorb heat from said otherbody andito pump said heat to said one body for liquefication -of a first zone or said one body adjacent said heat emitting thermojunction means, and second thermoelectric heat pump means mounted for relative movement with said first heat pumpmeans longitudinally of said bodies and having heat emitting thermoju'nction means-in good I heat transfer relation with said other body and having heat absorbing thermojunction means in good heat transfer relation with said one body, said second-heat pump means being operable when'en'ergized to absorb heat from said one body and to pump saidheat to said other body s for liquefication of a second zone, of said other body adjacent said last-mentiohedheat emitting thermojunction J means.

9'. In apparatusfor zone refining of a pair of bodies of solid material without-substantial loss of the latent heat 7. of fusion of said; material, receptacle means for said bodies comprising oppositely disposed spaced parallel first and s'econd'wall portions of good thermal conductivity respectively in good thermal contact with one and the other of said bodies, a first thermoelectric heat pump 'mounted'for relative movement longitudinally, of ,said

bodies and parallel with said walls and having heat .emitting'thermojunction means in good thermal contact 'with said firstwall portion and having heat absorbing 'thermojunction means in good thermal contact with said second wall portion, said first heat pump being operable when energized to absorb heat'fror'n .said other body through said second wall portion and to pump said heat to said one body through said first wall portion for'liquefication of a first zone of said one body adjacent said heating emitting thermojunction means, and a second thermoelectric heat pump mountedsfor relative movement 1 with said first heat pump longitudinally of said bodies and iparallelwith'said walls and having heat emitting thermosaid second wall portion for liquefication of a second zone 55 of said other body adjacent said last-mentioned heat emitting the'rmojunction means.

10. Apparatus for zone refining of a pair of elongated bodies of solid material comprising, first thermoelectric heat pump means having heatvemitting thermojunctionh means in good heat transfer relation with one ofsaid bodies and having heat absorbing thermojunction means in good heat transfer relation with the other of said bodies, said first heat pump means being operable when energized to absorb heat from saidother body and-t0"*""- pump said heat to said one body forliquefi cation of a first zone of said one body adjacent said heat, emitting thermojunction means, second thermoelectric heat pump means having heat emitting thermojunction means in good heat transfer relation with said other body andhavir'ig, heat absorbing thermojunction means in good heattrans fer relation with said one body, said second heat'pump means being operable when energized to absorb heat from said one body and to pump said'heiat to said other body for liquefication of a second zone of said other body adjacent said last-mentioned heat emitting thermojunction means, and means for effecting gradual movement of both of said heat pump means longitudinally of saidbodies to effect corresponding movement of said first and second liquefied zones.

11. Apparatus for zone refining of apair of bodiesof solid material comprising, receptacle means for said bodies comprising oppositely disposed spaced parallel first and second wall portions of good thermal conductivity respec-' tively in good thermal contact with one and the other of said bodies, a first thermoelectric heat pump having heat emitting thermojunction meansin good sliding andrther-s mal contact with said first wall portion and having heat absorbing thermojunction means in good sliding and thermal contact with said second wall portion, said firstheat pump being operable when energized to absorb heat from said other body through said second wall portion and to pump said heat to said one body through said first wall portion for liquefication of a first zoneof said one body 7 adjacent said heat emitting thermojunction means, a sec- :ond thermoelectric heat pump having heat emitting thermojunction means in good sliding and thermal contact with said second Wall portion and having heat absorbing? the'rmojunction means in good slidin g and thermal contact with said first wall portion, said secondheat'pumps.

being operable when energized, to absorb heat 'fr'om'said onebody through said first wall portion and to pump said 5 heat to said other body through said second wall portion for liqueiication of a second zone of said other body adacent said last-mentioned heat emitting thermojunction I means, and means 'for elfecting gradual movement ofsaid heat pumps to cause sliding engagement of said thermojunct ion means along said wall portions and corresponding movement of saidfirst and second liquefied zones.

References Cited in the file of this patent UNITED STATES PATENIS 7 Lindenblad Sept. l1, 1956 Bichowsky 4-; A 21 1953-,

UNITE STATES PATENT OFFECE Patent No. 2 937 2l HEQATE @F QREQ lifiN May 17 1960 Robert We v Fritts et ale It is hereby certified that ent requiring correction and the corrected below.

Column 41 column 6 lines 52 and 55 read liquefieation e Signed and sealed (SEAL) Attest:

ERNEST W. SWIDER Attesting Officer line 26 after usual error appears in the above numbered patt the said Letters Patent should read as freezin ii; each occurrence insert for '1iepiefeetion 5th day of September 1961.

DAVID L. LADD Commissioner of Patents USCOMM-DC Patent N0a 2. 93T 2l6 May 1? Robert W.o I Fri'firfigs e ale It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 41 line 26 after usual insert freezing column. 6 lines 52 and 55 for "'liopzzefeeeioh each 0eeurrehce. read llquefiea'ition u Signed and sealed this 5th day of Sep'eemi'oer i961.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents USCOMM-DC 

